1. Field of the Invention
This invention relates to a process for producing a polyurethane foam, more particularly to a process for producing a rigid polyurethane form by a one-shot process and a composition used for producing such a polyurethane form.
2. Description of the Prior Art
Polyurethane forms are produced by using a polyol, a polyisocyanate, a blowing agent and a reaction accelerator in a open vessel. In order to produce a rigid polyurethane foam having excellent heat resistance by this process, there is used as polyol an alkylene oxide adduct of 4,4'-diaminodiphenylmethane. But when a rigid polyurethane foam is produced by using the above-mentioned compound as polyol, the resulting polyurethane foam has a defect of haivng poor impact resistance. Further, when the above-mentioned compound is used as polyol by employing the one-shot process in a closed vessel, no sufficient rigid polyurethane foam is produced due to poor flow properties.